I don't see that T said anything reprehensible.

I found your email to him rather harsh and somewhat accusatory (e.g. I pay for your time, so think of me and/or do as I say).. Ouch. Much to his credit (and I wonder how many Ts would be able to do so) he remained professional, rather than defensive. He also made it clear that you may not approve of his behaviour but he does not have to comply and satisfy every client's wish. For me, that is a respectful boundary setting that he exemplified rather than automatically giving in to clients. He has made a lot of effort to accommodate you in the past but standing up or not, does not warrant such a reaction.

It seems (from the email exchange) that you were putting him on the spot: I am hurt, sad, so change! Why should he change..? You guys may talk about it but it comes across more like an over-reaction to a trivial behaviour and a demand to change.

Explore the cause by all means but he (or anyone else) really shouldn't change how they are if they are not doing anything wrong, or if they are not comfortable doing so.